Three chronic conditions were examined--acute alcohol intoxication, seizure disorder, and respiratory illness--to quantify the extent of repetitive emergency medical services (EMS) use in a defined population. Urban EMS system ambulance data from 1992 to 1994 were analyzed for the three designated conditions with respect to transports by condition and individual patient. Analysis by chi2 was used for comparing proportions. Analysis of variance after square root transformation was used to evaluate differences among means. The total number of transports analyzed was 15,541: 7,488 for acute alcohol intoxication, 4,670 for respiratory illness, and 3,383 for seizure disorder. These transports involved 8,692 patients who were transported at least once for one of the three designated conditions. The mean number of transports for alcohol was 1.96 (95% confidence intervals [CI]: 1.92, 2.01), seizure 1.32 (95% CI: 1.27, 1.36), and respiratory 1.18 (95% CI: 1.15, 1.21). Of 369 patients transported five or more times during the study period, 260 (70.5%) were for alcohol, 56 (15.2%) for seizure, and 53 (14.4%) for respiratory complaints. This group comprised only 4.3% of patients, but 28.4% of all transports. Acute alcohol intoxication resulted in more repetitive ambulance transports than either seizure disorder or respiratory illness. A small number of patients were responsible for a large number of transports. Focused intervention for patients with high ambulance transport deserves further study.